In spite of numerous studies, there is much uncertainty about tautomerism innucleic acids and specifically cytosine. In the gas phase, form 2 dominates but ?G maybe about 1 kcal/mol for both 1 and the �rare� form 3. Spectroscopic studies �see� them but in much smaller abundance. The UV spectrum is normally assigned to 1. Dimerization may also influence tautomerization.Fig. 1. Selected isomers and a dimer of cytosine We present infrared and UV spectroscopic measurements in Ar matrix and discuss them by MP2 and CC quantum chemical calculations, including electronic excitations. Contributions from isomers/tautomers and/or dimers to the spectra are discussed.

New questions about tautomerism in cytosine: Quantum chemical and matrix isolation spectroscopic studies

240th National Meeting (2010)

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